Both wireless networks and the Internet protocol (IP) networks are extremely important in providing communications. While each type of network is important by itself, both types of networks are synergistic. Consequently, wireless networks and IP networks are merging with the evolution of communications. A wireless network utilizes a radio access network (RAN) in order to communicate with mobile terminals. A radio access network typically comprises base transceiver stations and a corresponding transmission network that interconnects the base transceiver stations. The transmission network enables a communications controller to instruct the base transceiver stations and to transport information to and from the mobile terminals. With the merging of wireless networks and IP networks, IP networks may support the functionality of the transmission network. A radio access network that utilizes IP for interconnectivity is often referred as an IP radio access network (IP-RAN). The IP radio access network is a comprehensive network solution that unifies different radio access technologies and enables ubiquitous third generation services. It may encompasses wideband code division multiple access (WCDMA) radio access network (UTRAN), GSM/EDGE radio access network (GERAN), wireless local area networks (WLAN), broadband radio access networks (BRAN), wireless Intranet office networks, and wireless home networks. The IP radio access network provides a single, cost effective and easily managed transport network linking all radio access networks.
IP networks deployed today are focused primarily on connectivity and typically support only one class of service with a best effort approach. The current IP protocol is connectionless and has an inherent degree of survivability. Dynamic routing protocols are used to react to faults by changing routes when routers learn about topology changes via routing information updates (e.g. link status advertisements). Current routing algorithms are very robust and survivable. However, the recovery time can be significant, on the order of several seconds or minutes, which can cause service disruption and loss of quality of service (QoS). This can be unacceptable for the IP radio access network, especially if its transport layer is connection-oriented which is more vulnerable to faults.
There are various factors that necessitate a protection/restoration scheme in the IP radio access network. First, Layer 3 (e.g. IP) rerouting may be too slow for radio access networks that need to support high reliability and availability. Second, physical and link layer protection mechanisms may not be deployed in topologies that meet carrier's protection goals. Third, the granularity at which the lower layers (typically at first and second layers, corresponding to the physical layer and the link layer, respectively) are able to protect traffic may be too coarse for the traffic requirements. Physical and link layer mechanisms have no visibility into higher layer operations. Thus, while physical and link layer mechanisms provide link protection, the mechanisms cannot provide node or traffic class protection. Fourth, the recovery approach of a connectionless network has several undesirable attributes. For instance, a forwarding path for recovery can be affected by the transient instability of dynamic shortest path first routing when failures occur. In practice fault restoration capabilities can be implemented in multiple protocol layers such as automatic protection switching in the physical layer, self-healing in the ATM layer and fast rerouting in the Internet protocol/multiprotocol label switching (IP/MPLS) layer. Usually, fault recovery is attempted first in the lower layers and escalated to higher layers if recovery is not possible.
Prior art protection options in the radio access network are limited. Protection schemes (if available) are based on lower layer protection mechanisms and dependent on the technology used in these layers. Moreover, protection schemes often utilize 100% redundancy in order that a network merely switches to the redundant facilities when a fault is detected.
Thus, there is a need to enable an IP radio access network to quickly recover from network failures. The recovery should be consistent with a grade of service that is associated with the effected wireless user and should provide protection on an economical basis.